Background: The Hypertension in the Very Elderly Trial ( HYVET) is a placebo controlled double blind trial of treating hypertension with indapamide Slow Release ( SR) +/- perindopril in subjects over the age of 80 years. The primary endpoints are stroke ( fatal and non fatal). In view of the fact that thiazide diuretics and indapamide reduce urinary calcium and may increase bone mineral density, a fracture sub study was designed to investigate whether or not the trial anti-hypertensive treatment will reduce the fracture rate in very elderly hypertensive subjects. Methods: In the trial considerable care is taken to ascertain any fractures and to identify risk factors for fracture, such as falls, co-morbidity, drug treatment, smoking and drinking habits, levels of activity, biochemical abnormalities, cardiac irregularities, impaired cognitive function and symptoms of orthostatic hypotension. Potential results: The trial is expected to provide 10,500 patient years of follow-up. Given a fracture rate of 40/1000 patient years and a 20% difference in fracture rate, the power of the sub study is 58% to detect this difference at the 5% level of significance. The corresponding power for a reduction of 25% is 78%. Conclusion: The trial is well under way, expected to complete in 2009, and on target to detect, if present, the above differences in fracture rate.